Cam controlled stretch former



July 7, 1959 a. F, RAYNl-:s 2,893,460

CAM coNTRoLLED STRETCH FORMER Filed Feb. l5, 1954 .5 Sheets-Sheet 1 INVENTOR. 4 6./.kA YN!! July 7, 1959 B. F. RAYNES 2,893,460

CAM CONTROLLED STRETCH FORMER Filed Feb. 15. 1954 3 Sheets-Sheet 2 INVENTOR.

l; PA YNI July 7, 1959 Filed Feb. l5, 1954 B. F. RAYNEs 2,893,460

CAM CONTROLLED STRETCH FORMER 3 Sheets-Sheet (5 IN1/EN TOR. 6.1: PAYNE! CAM CONTROLLED STRETCH FORMER Burt F. Raynes, Chula Vista, Calif., assignor to Rohr Aircraft Corporation, Chula Vista, Calif., a corporation of California Application February 15, 1954, Serial No. 410,229 4 Claims. (Cl. 153-40) This invention relates to a means for accurately controlling the amount of stress applied to a workpiece while it is being formed in a metal forming machine of the type wherein the workpiece is first stressed a predetermined amount and then formed while under tension by being wrapped along the face of a forming die.

' When forming metal on a machine of the aforemen- `tioned type, it has been customary to test a sample of the material to be formed to determine the amount of tension which must be `applied to the workpiece to stress 'it'.to its elastic limit. The necessary amount of tension, as determined from this test, is applied to the workpiece which is then wrapped along the face of a forming die to form it to a desired shape. In actual production practice, however, it has been found that the amount of tension required to stress a given number of workpieces of the same size and material to their elastic limits, may vary greatly. For instance, it has been found that one piece may require the application of a 40,000 pound force to stress it to its elastic limit while another piece may require as much as 60,000 pounds force to stress it to its elastic limit. In order to produce satisfactorily formed parts in a situation such as this, it would be necessary to test each workpiece to determine what tension must be applied to stress it to its elastic limit, a procedure obviously prohibitive from a cost and manufacturing standpoint. If, as an alternative, an average force ,is taken as a norm, as for example 0,000 pounds, it will result in some of the workpieces being greatly overstressed and others understressed, resulting in a complete lack of uniformity in the iinished parts and rendering many of them useless. Also, since in many instances the yield strength and the ultimate strength of a workpiece are relatively close values, it follows that any appreciable amount of over stressing of a workpiece will result in failure of the material and ruining the workpiece.

While the amount of tension required to stress each of a number of workpieces of the same size and material to their elastic limits may vary greatly, it has been found that the elongation of each workpiece when stressed to Vits elastic limit, is very nearly the same. It therefore vfollows that by determining the amount of elongation required to stretch a hard workpiece to its elastic limit, all other Workpieces of similar size and material whether in --highv or low tensile range of hardness may be stretched to their elastic limit by a substantially like'amount of elongation' despite the variation in the amount of force rep quired by each workpiece.

It is, therefore, the primary object of my invention to provide a control means for use'on a machine of the aforementioned type, to regulate the elongation of a workpiece to an amount suiiicient to stress it a desired amount and to maintain a proportional amount of elongation in proportion to the length of the unformed portion of the workpiece throughout. the forming operation.

1 A1 further object is to provide a control means as be- Aorementioned which is adaptable for useon, al1 types of ICC forming machines in which tensile stress is applied to a workpiece while it is being formed.

A further object is to provide a control means as above described which is simple and inexpensive to manufacture and which may be quickly and easily installed on a forming machine.

These and other objects and advantages will become Vapparent as the description of the invention proceeds.

My invention consists primarily of a cam control which is designed to operate in conjunction with the forming die to regulate the amount of tension applied to the workpiece by the tensioning device, prior to and during the forming operation, to permit the workpiece to be elongated a distance suiicient to stress it the desired amount at all times. 'Ihe shape and size of the cam is governed by the shape of the forming die with which it is used and the size and material of the workpiece to be formed.

For a better understanding of the invention, attention is directed to the accompanying drawing illustrating several preferred embodiments of the invention and in which:

Figure 1 is a front view of a forming machine having a hydraulic tensioning device regulated by a cam secured to and rotatable with a rotary table on which the forming die is mounted.

Figure 2 is a top view of the machine of Figure 1.

Figure 3 is a schematic view partly in section of a portion of the machine of Figure 1 showing its hydraulic system controlled by a cam.

Figure 4 is a top view of a forming machine employing two hydraulic tensioning devices which pivot about a stationary forming die, each of the tensioning devices being controlled by a cam mounted in a stationary position adjacent the die.

VFigure 5 is a front view of the machine of Figure 4.

Figure 6 is a top View of a forming machine in which the workpiece is stressed by rotation of a rotary table, illustrating a cam control for regulating the amount of stress applied during the forming operation.

Figure 7 is a front view of the machine of Figure 6.

Figure 8 is a top View of a forming machine wherein one end of the workpiece is held in a stationary chuck while the workpiece is drawn along the face of a stationary forming die by a tensioning device equipped with a control valve which regulates the elongation of the workpiece.

Figure 9 is a view, partly diagrammatic, illustrating the attachment of the tensioning device control valve.

Referring to the drawing, the forming machine illustrated in Figures 1 and 2 comprises a base 10 having a rotary die supporting table 11 which may be slowly rotated by a known power means as, for example, a worm and worm gear (not shown) and on which is mounted a suitably shaped forming die l2. A chuck 13 is pivotally connected to table 11 and adapted to grip the end 14 of a workpiece 15. A cam 16 secured to and rotatable with table 11 has a suitably curved face 17 whereby the tension applied to the workpiece is controlled in a manner to be later explained. A hydraulic cylinder 1S is attached to a vertical shaft 9 pivotally supported in a frame 8 attached to 'base 10 and contains a piston P. The piston is connected to the end of a piston rod 19 which has a' chuck 20 attached to the other end thereof and adapted to grasp the end 21 of workpiece 15, and serves as a means for applying tension to workpiece 15. Oil or other iuid under pressure is supplied to the head end of cylinder 18 through a conduit 22 connected to a suitable supply tank (not shown). Fluid under pressure is supplied to the rod end of cylinder 18 by a supply pipe 23 connected to the supply source through a control valve 24 attached to chuck 20. Fluid connection is established between pipe 23 and valve 24v through pipe 25, valve,2

P1 to apply sucient tension to workpiece 15 to elongate it the desired amount. As arms 43 and 44 continue to move` toward body 42,` workpiece 15 is wrapped along the face of die 12 and cam followers 38 and 381 moving along cam faces 17 and '171 control valves 24 and 241,

.in the manner previously explained, to regulate the amount of stress applied to the workpiece throughout the forming operation. The workpiece is continually stretched an amount which is directly proportional to the length of its unformed portion.

Referring to Figures 6 and 7, the forming machine illustrated therein comprises a base 10 having a rotary die supporting table 11 which may be rotated by a known power means (not shown) and on which is mounted on table 11 the chuck 13.1adapted to grip the end 14 of workpiece 15. A heavy cam 16 having a curved face 17 is secured to table 11 by bolts 51. A sleeve 52 pivotally mounted on base 10 slidably contains a shaft 53 to one end of which is secured a chuck 20 adapted to grip the end 21 of workpiece 15. A cam follower 54 adapted to engage cam face 17 is mounted on shaft 53 adjacent chuck 20. f

To operate the machine table 11 is rotated in a clockwise direction until chuck 13 is brought into a position sufficiently near chuck 20 so that ends 14 and 21 of workpiece 15 may be gripped by chucks 13 and 20 respectively. .Table 11 is then rotated in a countercllockwise direction asfndicated `by arrow A in Figure 6, moving chuck 13 vaway from chuck 20. As table 11 rotates moving chuck 13 away from chuck 20, shaft 53 and chuck 20 are drawn toward table 11 by workpiece 15 until cam follower 54 engages cam face 17 preventing any further forward motion of chuck and shaft 53. The continued notation of table 11 moving chuck 13 away from chuck 20 applies the tension necessary to elongate workpiece 15.

v When workpiece 15 is in position to contact die 12, as

slrown in Figure 6, it will be elongated an amount sucient to stress it the proper amount prior to wrapping it along the face of die 12. As table 11 continues to rotate, wrapping workpiece 15 along the curved face of die 12, the contour of cam face 17 is such that chuck 20 and shaft 53 are permitted to advance toward table 11 ata rate which will maintain the elongation of workpiece Y 15 constantly indirect proportion to its unformed length Y during the formingl operation.

Referring to Figures 8 and 9, the forming machine illustrated is similar inV construction to that previously described and illustrated in Figures 4 and 5. It consists of a main body member 42 having a pair of carrierarms 43 and 44 pivotally attached to one end thereof to pivots 45 and 46. A pair of draw bars 47 and 48 extending from arms 43 and 44 respectively, are connected to a suitable power source (not shown) to provide means for moving arms 43 and 44 about pivot points 45 and 46 toward body 42. Forming die 12 is mounted on the end .lof body 42 in a stationary position between and above arms 43 and 44. A chuck 13 adapted to grip the end 14 of workpiece 15 is pivotally mounted on arm 44. A hydraulic cylinder 18 is pivotally mounted on arm 43 and contains a piston P connected to a piston rod 19 to one end of which is attached a chuck 20 adapted to grip the end 21 of workpiece 15. Fluid under pressure is supplied to the head end of cylinder 18 through a pipe 22 connected to a suitable fluid supply source (not shown) and to the rod end of cylinder 18 through a pipe 23 and a control valve 56. Fluid connection is established between pipe 23 and valve 56 through pipe 25 and valve 26 and between valve 56 and the rod end of cylinder 18 through pipe 57. Valve 56 is of a known type which is normallyV opened and closed by pressure against a control lever 58. Valve 56 is adjustably supported on the endof cylinder 18 by a rod 59 slidably mounted in an lopening in a bracket 60 which is secured to cylinder 18 and a lock screw 61 serves to engage rod 59 to lock it in adjusted position.

To operate this machine, uid under pressure is directed by pipe 22 to the head end of cylinder 18 to move piston P to the rod end of the cylinder and move chuck 20 sufciently near chuck 13 so that ends 14 and 21 of workpiece 15 may be gripped by chucks 13 and 20 respectively. Arms 43 and 44 are then simultaneously moved about pivot points 45 and 46 toward body 42 to positions which permit full contact between wlorkpiece 15 and the face of die 12 as shown in Figure 8. Fluid under pressure is then directed to the rod end of cylinder 18 from pipe 23 through 25, valve 26, control valve 56 and pipe 57 causing piston P to move toward the head vend of cylinder 18 and retract rod 19 and chuck 20 to apply tension to workpiece 15 and stretch it. Valve 56 is set in an adjusted position so that when workpiece 15 has been elongated suiiiciently to provide the proper amount of stress to force it toV conform to the shape of die 12, chuck 20 will come in contact with control lever 58 and move it, thus closing valve 56 which stops the passage of uid into cylinder 18. The movement of piston P is thus arrested when the workpiece has been elongated the proper amount.

In each form of the invention, the length of workpiece between the chucks gripping its ends, before stretching, is kept the same for all workpieces to be bent to the same shape.

The fluid used in the hydraulic systems of the above described machines is preferably a liquid such as oil `and 'the pipes conveying the liquid to moving parts of the Y machines are composed of liexible material.

This invention may `be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment of the invention is therefore to be considered Y as in all respects illustrative and not restrictive, the scope t said table; means adjacent one end of said die connecting one end of the workpiece to said table; means for rotating said table to wrap the workpiece along said die face; a jaw gripping the other end of the workpiece; a fluid containing cylinder; means for supporting said cylinder so as to prevent movement thereof toward said die; a piston slidable in said cylinder and connected to said jaw; an outlet including a movable valve for permitting the escape of uid from the end of said cylinder adjacent said table; and means including a curved cam carried by said table and constructed to control said movable valve to permit the passage of fluid through said outlet at a desired rate as the table is rotated.

2. A forming machine adapted to conform a long workpiece to a desired curvature comprising, in combination, a die having a face conforming to said curvature, means including a pair of jaws respectively gripped to the ends of the workpiece and spaced from said die for holding the unformed workpiece initially away from the die, a cylinder, a piston connected to one of said jaws and slidable in said cylinder, means supporting said cylinder and die for relative rotation therebetween sufficient to bring the workpiece into contact with the die 'with' theirdief'sid" cami'iface i`being""f`rther shaped to control fcontinual elongation" ot`,"'thewbrkpieee" bysaid "cylinderanddieyanduworkpiece tensioning means intensioning means proprtion"to".the"length ofi the Y"'*cluding 'said' pistonandcylinder and a camV and followerl UHWIaPPed portion ofi'thWOlkPiCe" 'aSheWOrkpeC *therefor carried respectively by said die'and 'said' one 5f is"wrapped' alongwthe 'face'of the clietsaid tensioning of' 'the jaws for resisting'movementvv of said piston to- Ill'allSf/lIiCll-l'dillg a'ValVe`Clied by Said 011e' fihe J'aWS ward'the die as said' one'of'the jaws andthe portionlof Hand having aspring biased1 plungermovablennder conthe workpiece gripped thereby are drawn towardthedie Awtrol kofsaid'follower Vto aiirstY position" for preventing inresponseto"movement 'of'theworkpiecetinto .contact ""'release'of fluid*'urdenpressure by' said? piston in said ""with ithe die and Vsubsequentwrapping thereabout, said 10' CY11df`a1d O a `SeonffPSIOI' lfeleasng'sad lld "carn'having'a curved face and said followerfbeing conv-l`fromthecylindertolgaerrnitmovementioflthepiston to- -`4strained by said tensioning means to contactV and follow `VWard the die. v "along'said' faceofthe cam asthe workpiece'is brought 4.' A` forming m'achine adapted 'to"'confoxm along --rints'ontact with and wrapped along said face-ofithe "wo'rkpiece' to adesirdteurvature"comprising, in comidie, said'cam `face being shaped'to controlv initial stretch- 15 binationg a Yrotary table', a 'die having a face'conforming ""ing'ofsaid workpiece` by said tensioning 'means'prior'to 'to' said"curvatureand supported'on said table`for"rota fcontactingof'the workpiece withthe die,A said earn face tiontherewith,=means 'including 'apair' vof jaws-respecl`"being furthershaped to'control continual elongation'of tively gripped t0 hVelil'dS'Of'ithe' Wbfkpiecead spaced y'the'workpiecze by said tensioning4 means in proportion `lfrom-said die for'holding: therunformed workpiece int*to* the llength of `the 'unwrapped vportion of ithe work-"20 itially' away' f1'0mthe`die; aACYlDdeF" meallSOl SUP- `pieceastthe workpiece isv wrapped al0ng-the face ofthe porting said cylinder'forrotation about atransverse axis ""'die; said tensioning means including afvalve carriedgby i parallel' tothe-axisofrotation` of'said table, a'piston 'fsaid'one of the jawsand having a'spring'biased plunger "connected'to one of said-jaws"andislidable in said cyl- "movable undercontrol of said followerto afrst posiy "ilderfmealls' SGCUIHgIheheI f 'Said aWS "Y'Said "tionf-forlpreventingv release" of uid underpressure 'by' 25' table,means for' rotating theltabletobring-thework- "said'piston in said cylinder and` to a` secondposition for Piece'into 'COntaCt withthe dieand Wrap 1111"W0fkpiece v`releasing said uidfrom the cylinder to' permit'movevalong said'face* of -the "'die;` and; workpiece `tensioning *rnentlot the piston toward the die. `^means'including said 'piston and cylinder andr a-cam` and 3. A formingnmachine adapted; tov 4rconform atlong "'"follower"therefor'carriedffrespectivelv by said table and workpiece to a desired curvature comprising, in cornB() said one of the jaws for resisting movement of` said `fibination, a rotary table, a diehaving a 'face 'conforming piston toward-the die as'fsaideone'fofthefjaws and the 'ftosaid curvature' and supported on said table for' rota- '-'portion' of@theworkpiecegrippedl'fthereby are drawn vtionx therewith, means including a-`par ofjaws respec- "toward thediedntresponse'to-'movement of-theworktively gripped to the ends of the workpiece and spaced v'vpiece'into 'contact'withthe die :and subsequent wrapping "fromsaiddiefor holding theV unformed workpiece Vin-"35Vthereabont; -said cam having aAk curvedf-face--and said --itially away from thedie, a cylinder, means'V for'sup- 4'followerffbeing constrainedby saidtensionng means to ""'andito-wrap the wo'rklgaieces-"alongsaid.V face of "the''die, nreansfor causing` vsaidY relative rotation' between "said porting said cylinder for rotation "about Y a' transverse axis parallel tothe axisv of rotation Vofsaid table,` a piston -connected to one of said jaws and slidable in said y cylinder, means securing'the other'of said jaws toysaid' -fo1lower therefor carried respectively byfsaid table and said one of thejawsfor resisting-movernent of said piston toward the die as said one ofthe jawsand'the *portion ofI the workpiece gripped thereby are drawn toward-the die in response to movement of the workcontact and lfollow along said face ofthe cam as the Y workpiece isbrought 1into^contact-with 1 andk wrapped along saidfacerof'thedie; said fcam' facebeing-shaped to control-initial stretching=`of said-@workpiece by said Yivvithfthe'dia-lsaid"carn' fac'e'being'further shaped to con- F'trol continual elongation Vo-theworkpiece :by said vten- -'-sioning-means in'` proportion? `to'the length -of the un- -wrappedportion of =the workpiece as'lthe'v workpiece .is

f Wrapped 'along' i the tace 'of thedie.

`References Cited-,in the lefof this. patent UNITED STATES APA'IIITS piecei into contact with the die-and subsequent wrap-:150 264,249 Yoder Apng()I 1918 klping-thereabout, said cam having a'curved facefand 1,963,010 vBailey .]u1y.311.1934 said follower being constrained by said tensioningmeans 2,370,329 Seifed 1:.eb427ty 1945 to contact and follow along said facel oflthe cam' as the 2,412,731 Hoifman .Dect 17, 1945 `-workpiece is brought into contact-with andlwrapped 2,514,830 -Bath julyll, 1950 along said face ofthe die, said cam face being shaped-55 to control initial stretching of Asaid workpieceby said Y FOREIGNPATENTS "tensioning means prior to contacting of.V theworkpiece 482,769 /Great`Britainl Apr. 5,1938 

